The present invention relates to a wind turbine-driven hydrogen production system for producing hydrogen by supplying electric power generated by a wind turbine to an electrolytic hydrogen production system and, more particularly, to a wind turbine-driven hydrogen production system which includes the wind turbine whose main circuit portions are mounted independent of a power system.
Today, most of energies sustaining our life are supplied from fossil fuels. However, there is the problem that the resources will be exhausted. In addition, there is the problem of environmental crises such as global warming. One conceivable method of solving these problems is to exploit a renewable energy such as wind power, solar energy, or water power.
Renewable energies such as wind power generation have the disadvantages that the power densities are low and supply of energy is unstable. One method of solving these problems consists of once converting energy into hydrogen, i.e., a secondary energy, storing it, and supplying the hydrogen in response to energy demand, thus achieving stable supply of energy. Hydrogen energy also has the advantage that it can be stored more easily than electrical energy. A hydrogen production system which produces hydrogen by generating electric power with a wind turbine and supplying the generated electric power to an electrolytic hydrogen production system has been created from these viewpoints.
Generally, sites where wind turbines are installed must satisfy the requirements: (1) the sites are in good wind conditions; and (2) land sites where wind turbines can be installed are secured. Remote rural areas, isolated islands, and offshore sites may be highly potential candidates for such sites. However, at such sites, a power system for connecting the wind turbines may not be present, in which case the generated electric power cannot be transmitted. Furthermore, if a power system exists, such sites are remote from the main power system. Therefore, the system equipment does not often have a capacity to transmit electric power generated by wind turbines. This point hinders introduction of wind turbines. If a hydrogen production system which produces hydrogen with electric power generated by wind turbines and stores the hydrogen is available, any power system for transmitting electricity is not required and so it is possible to make efficient use of the wind turbines.
One method for use with a hydrogen production system utilizing wind turbines is proposed to especially enhance the efficiency of production of hydrogen. When the wind speed is less than the nominal (rated) wind speed for the wind turbines, the hydrogen production system is controlled with a constant voltage, and the load is divided. When the wind speed is higher than the nominal (rated) wind speed, the system is controlled with a constant current. The contents of this technique are described in JP2005-27361, paragraph 0004.
JP2004-269945, especially from paragraph 0008 to paragraph 0011, states a method for enhancing the efficiency of production of hydrogen of a hydrogen production system utilizing wind turbines. The wind turbines are controlled at a rotational speed at which the efficiency of power generation of the wind turbines is maximized within a range of wind speeds. The hydrogen production system is controlled with a constant voltage.
A method of controlling a voltage for maximizing the efficiency of power generation of wind turbines in a hydrogen production system utilizing these turbines is described in JP2005-073418, paragraph 0008.
Where wind turbines are installed independent of a power system and electric power generated by the turbines is supplied to an electrolytic hydrogen production system to produce hydrogen, any power system acting to absorb variations in the output from the wind turbines does not exist. Therefore, the rotational speed of the wind turbines vary greatly and goes beyond the operable range and thus the power generation stops. As a result, the operation time of the wind turbines is shortened, reducing the amount of produced hydrogen. Furthermore, where a hydrogen production system consisting of wind turbines and an electrolytic hydrogen production system is installed independent of a power system, the power supply for controlling the hydrogen production system cannot be used from the system at start-up of the turbines and, therefore, self-starting cannot be done.